This invention relates to the use of catalyst system for the polymerization of olefins, particularly, to catalyst system comprising supported, often with MgCl2, Ziegler-Natta catalyst which has been modified with an amine, preferably during synthesis. The catalyst system is used to polymerize monomer having at least one Ziegler-Natta polymerizable bond, particularly olefin, especially xcex1-olefin, such as ethylene, propylene or their combinations with or without other monomer.
It is known that polyolefin manufacturing or production processes typically involve the polymerization of olefin monomer with an organometallic catalyst of the Ziegler-Natta type. Catalyst systems for the polymerization of olefins are well known in the art. Generally, these systems include a Ziegler-Natta type, which may be called a conventional or multi-site, polymerization catalyst component and a co-catalyst, often an organoaluminum compound. Examples of such catalyst systems are shown in the following U.S. Patents the disclosures of which are hereby incorporated by reference.
It is known that Cp2TiCl2 in the presence of alkylaluminum compounds polymerizes ethylene but not propylene whereas in the presence of methylalumoxane (MAO), Cp2TiCl2 polymerizes propylene also to produce atactic polypropylene. Combination of dimethyl titanocene and its Cp-substituted analogues and TiCl3 for propylene polymerizations has been reported in U.S. Pat. No. 2,992,212 and by G. A. Lock in xe2x80x9cThermoplastic Elastomers Based on Block Copolymers of Ethylene and Propylenexe2x80x9d, Advances in Polyolefins (Seymour, Raymond B., ed.) at pages 59-74. MAO was not used in this polymerization.
Typically catalysts for traditional polymerization of olefin monomer include a Ziegler-Natta-type polymerization catalyst component, a co-catalyst which is generally an organoaluminum compound, and an external electron donor or selectivity control agent, often an organosilicon compound. Such catalysts are described in U.S. Pat. Nos. 4,107,413; 4,294,721; 4,439,540; 4,115,319; 4,220,554; 4,460,701; and 4,562,173.
A Ziegler-Natta type polymerization catalyst is basically a complex derived from a halide of a transition metal, for example, titanium, chromium or vanadium with a metal hydride and/or a metal alkyl, typically an organoaluminum compound, as a co-catalyst. The catalyst is usually comprised of a titanium halide supported on a magnesium compound complexed with an alkylaluminum co-catalyst.
Our invention provides, at least, new Ziegler-Natta type polymerization catalyst with useful characteristics and ability to make useful polymer.
Use of our catalyst and practice of other aspects of our invention also yields useful and unusual polymer properties in polymerization processes using a supported Ziegler-Natta catalyst which has been modified with an amine compound.
We also provide, with this invention, ability to produce Ziegler-Natta polymerized polymer having low molecular weight and narrow molecular weight distribution.
Additionally, our invention improves catalyst activity by modifying the catalyst, usefully this is performed during synthesis.
These and other objects are accomplished by use of catalyst system comprising a supported Ziegler-Natta catalyst modified with Group 15 compound, preferably amine, in polymerization process for polymerizing monomer having at least one Ziegler-Natta polymerizable bond, notably olefins, especially ethylene.